Snow and nitrogen manipulation do not alter the dominant role of fungi in the N2O production of biocrusts in a temperate desert

Abstract

The impact of global climate change and human-induced nitrogen (N) deposition on winter weather patterns will have consequences for soil N cycling and greenhouse gas emissions in temperate deserts. Biological soil crusts (referred to as biocrusts) are crucial communities in soil and significant sources of nitrous oxide (N₂O) emission in desert ecosystems and are sensitive to environmental changes. The contribution of bacteria and fungi to N₂O production in drylands has been acknowledged. However, the effect of changes in snow cover and N deposition on the N₂O production of different microbial groups of microorganisms is not yet clear. In this study, we examine the responses of fungi and bacteria mediated pathways involved in soil N₂O production from biocrusts to long-term snow cover manipulation and N addition experiments in the Gurbantunggut Desert. These soils were incubated and subjected to biocide treatments (such as cycloheximide and streptomycin, and fungal and bacterial inhibitors), after which rates of potential nitrification and N₂O production were measured. Compared with controls, snow removal treatments from bare sand, lichen crust and moss crust reduced background rates of N₂O production by 29.41 %, 26.21 % and 20.49 %, respectively; N₂O production rates were 1.53-fold higher in bare sand, 1.38-fold higher in lichen crust, and 1.56-fold higher in moss crust after N addition. The addition of streptomycin significantly reduced the potential nitrification rates of bare sand and biocrusts, indicating that bacteria may be important sources of NO₃⁻ production in biocrusts rather than fungi. Conversely, fungi were main sources of N₂O production in biocrusts. Additionally, fungi also played a major role in N₂O production in biocrusts after snow cover manipulation and N addition. Both snow cover manipulation and N addition treatment indirectly affected the N₂O production in biocrusts by considerably affecting the content of substrate N and the abundance of microbial groups. Our research suggests that fungi are main contributors for denitrification in biocrusts, and that snow cover changes (removal snow and double snow) and N addition alter the contribution of biotic pathways responsible for N cycling.